NAME

ORTE_SNAPC - Open RTE MCA Snapshot Coordination (SnapC) Framework: Overview of Open RTE's SnapC framework, and selected modules. Open MPI 3.1.3

DESCRIPTION

Open RTE can coordinate the generation of a global snapshot of a parallel job from many distributed local snapshots. The components in this framework determine how to: Initiate the checkpoint of the parallel application, gather together the many distributed local snapshots, and provide the user with a global snapshot handle reference that can be used to restart the parallel application.

GENERAL PROCESS REQUIREMENTS

In order for a process to use the Open RTE SnapC components it must adhear to a few programmatic requirements.

First, the program must call ORTE_INIT early in its execution. This should only be called once, and it is not possible to checkpoint the process without it first having called this function.

The program must call ORTE_FINALIZE before termination.

A user may initiate a checkpoint of a parallel application by using the orte-checkpoint(1) and orte-restart(1) commands.

AVAILABLE COMPONENTS

Open RTE ships with one SnapC component: full.

The following MCA parameters apply to all components:

snapc_base_verbose: Set the verbosity level for all components. Default is 0, or silent except on error.

full SnapC Component

The full component gathers together the local snapshots to the disk local to the Head Node Process (HNP) before completing the checkpoint of the process. This component does not currently support replicated HNPs, or timer based gathering of local snapshot data. This is a 3-tiered hierarchy of coordinators.

The full component has the following MCA parameters:

snapc_full_priority: The component's priority to use when selecting the most appropriate component for a run.
snapc_full_verbose: Set the verbosity level for this component. Default is 0, or silent except on error.

none SnapC Component

The none component simply selects no SnapC component. All of the SnapC function calls return immediately with ORTE_SUCCESS.

This component is the last component to be selected by default. This means that if another component is available, and the none component was not explicity requested then ORTE will attempt to activate all of the available components before falling back to this component.